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DEPARTMENT OF COMMERCE 
BUREAU OF FISHERIES 

Economic Circular No. 46 ::::::::: : : Issued February 20, 1920 

CLAM RESOURCES OF THE TEN THOUSAND 
ISLANDS, FLA." 



The large hard clam, Venus mercenaria mortoniy found on the west 
coast of Florida is quite similar, except in size, to the familiar hard 
clam or quahaug of the Atlantic coast. '' Since the hard clam is one 
of our most valuable food mollusks, information relative to tho 
resources of the extensive clam beds found in the region of the Ten 
Thousand Islands, Fla., is worthy of dissemination. 

EXTENT OF CLAM BEDS. 

These beds are situated off the shore of the Ten Thousand Islands, 
extending, generally speaking, northward from Cape Sable, near the 
southern end of the west coast of Florida, to (lullivans Bay, which is 
a little south of the city of Caxambas, A natural clam bed extends 
from Shark Point to Gullivans Bay, a distance of 35 miles. The 
inner edge of this bed is about one-eighth mile from shore; and the 
outer, at least 5 miles offshore. It is safe to say that the natural bed 
of clams situated off the Ten Thousand Islands comprises at least 150 
square miles of bottom. 

The shores of the Ten Thousand Islands slope vei-y gradually into 
the Gulf. At a distance of 1 mile offshore the water is about 4 feet 
deep, and for the next 8 or 10 miles the slope is about 2 feet to the 
mile. There are places situated within a mile of the shore where bars 
are exposed at low tide, and it is about these burs that the hand 
fisherman secures his catch by means of "treading''; that is, step- 
ping on clams with the bare feet and then drawing them from the 
bottom by means of a two-tined fork with a handle 6 inches in length. 

The entire 150 square miles of clam bottom is practically one large 
bar, the clams being equally as plentiful in water 1-2 feet "deep as on 
the shallow bars in water 2 feet or less in depth. Clams in these 
deeper places are inaccessible to the hand fisherman, since tongs are 
not used in this locality. The clams are so abundant, however, that 
an average fisherman can dig 250 per hour in the three or four hours 
during which the tide usually permits him to work. 

« Based on reports by William C. Shroeder, fish culturist, U. S. Bureau of Fisheries 

""The life history of the hard clam or quahauR, VenuK mereermria, of the Atlantic coast 

is described by Dr. D. L. Beldlng In the Quahaug and Oyster Fisheries of Massachusetts 

published by The Commonwealth of Massachusetts (Wright & Potter State printers' 

Boston). ' 

160087—20 



2 -U^ 

The only places where clams were not found in large quantities 
were at the mouths of the various rivers and " runs " and in the area 
within about one-eighth mile offshore. There were certain places, 
however, where clams were abundant within a few hundred feet of 
the shore. North of Coon Key tliere are practically no clams near 
shore, while from south of Lossman's Run almost to North West 
Cape they may be found in scattered areas. 

ABUNDANCE OF CLAMS. 

The most important shallow bars are located off the following 
places: Coon Key, Rabbit to Pavilion Key, Clam Point, Alligator 
Point, and Lossman's Run. These bars also comprise the northern 
and southern limits of the major clam bar. 

Over most of the bed clams are found in numbers varying from 
5 to 20 per square yard. In some places they are evenly scattered 
about, while in others they are grouped together closely with inter- 
vening barren patches. When they are found in this latter condition 
the barren patches are never large, usually a few square yards in 
extent. 

Tlie results of de^ailed examinations of various representative 
portions of the bed follow : 

One and one-half uiilcs northca-ft of Cape Romano (near Coon Key) ; depth of 
Jcater 7 feet. — In a lew moment.s i'our cliiins were lir()ii.i.';lit aboard. Clams 
could be felt with the sponge hook in all places which could be touched from 
the boat. 

One mile south of Coon Key, irithin a fcir hundred feet of the Pyramid 
TJijht ; depth of irater 6 feet. — In about 10 niimitcs ei^^ht clams were brought 
aboard. Clams were plentiful. 

Tiro and one-fourth mite-'i southeast of Coon Keii: deptli of irater S feet. — 
Plenty of clams were felt with the hook. 

Off Horse Key. elose to shore. — No clams were felt. (In most cases clams 
wei-e not found within one-eighth mile offshore, but invariably they were found 
beyond that distance.) 

Round Key. — Close to shore very few clams wei-e found. ()ffshort» one-half 
mile they were plentiful. 

Tifier Key and Panther Key, offshore one-half mile. — Clams were plentiful. 

Rabbit Key to Parilion Key. — Between these two keys clams were found to 
be very plentiful. A bar lies midway between, being fully 1 square mile in 
area. The pilot, l>y treading, dug 84 clams in 20 minutes. They were more 
plentiful, however, than this observation would seem to show, since the water, 
being about 2i feet deep, impeded operations somewhat. In a short time 35 
clams were taken by tisliing from the boat with a sponge hook. They averaged 
fully ^ to 10 per square yard at this place. 

Parilion Key, r>ff>ihore one-quarter mile. — Clams were fairly x>lentiful. Oflf- 
^hore 1 mile clams were very plentiful. 

Bird Rock, about 3 miles southe)ast of Parilion Key. — One-tentli mile off- 
shore clams were fairly plentiful. Three-fourths mile off Bird Rock clams were 
very plentiful. Twelve were dug with a sponge hook within a space of 1 
S(iuare yard. 

Clam Point, one-quarter mile south of Bird Roek. — Clams were exceedingly 
plentiful. Three men dug 300 in 30 minutes by treading. At this point the 
bottom is exposed in part during very low tides. The bottom is covered with 
a thick growth of eel grass in which the clams were very numerous. The clam.s 
here averaged from G to 15 per square yard, ranging in size from those known 
to the trade as "little necks" to large ones weighing 4 pounds or more. This 
bar is about one-half square mile in ar^a. 

Seminole Point. — Clams were plentiful. 

Alligator Point, three-fourths mile offshore. — Here lies a large bar, about 1 
square mile in area, whereon, of all places, clams were the most plentiful and 
accessible. It is here tluit the few clam.tishermeu usually opei-ate. Off this 



. bar two men secured a cai'so of 3,500 large clams in twc) to three tides (8 to 
rl2 hours). It is claimed that from an area of about 10,(X)0 square yards 37,000 
clams were dug between Mny and November, 1918. 

Slightly offshore from Alligator Point.— One of the cannery's dredges is 
claimed to have dug, within an area of about 1 square mile. 250 bushels of 
, ! clams almost daily for four years. Over this place where the dredge was sup- 
ir: posed to have operated, clams were found in quantities sufficient to warrant 
- : digging. In fact, it could scarcely be noticed that any clams had been re- 
moved, excepting that those found were somewhat smaller on an average than 
those found in other places. Thus it can readily l)e seen what enormous 
quantities of clams may be found off the Ten Thousand Islands. 

From Alligator Point to Lossnian's Run. — Clams were plentiful. The Ten 
Thousand Islands and the major portion of the clam bar teruiinate at I.,oss- 
man's Run. A few clams were found in scattered areas almost to Northwest 
Cape. 

SOIL. 

The soil has a decided influence on the presence and abundance of 
the cdams. Through many tests it has been found that the soil best 
fitted for these clams is composed of sticky mud in which eel grass 
thrives. Forty separate tests were made over a distance of 50 miles 
in order to discover the abundance of the clams and the character of 
the soil. It was found that of the 10 places where clams were most 
abundant 8 contained eel grass, while of the 30 places containing few 
or no clams only 1 contained this grass, and this was very close to 
shore. As a rule the harder the bottom the fewer are the clams. 
On an entirely sandy bottom they do not thrive; but they are rather 
abundant in places containing a mixture of sand and mud. This 
sticky mud soil usually contains more or less broken shell and is 
firm enough to keep a person walking upon it from sinking more than 
a few inches. 

WATER. 

The water about the islands is muddy, due probably to the cur- 
rents moving over the muddy bottom. The salinity, at the time of 
investigation. May, 1919, was very high — the density readings rang- 
ing from 1.026 to 1.0292 — probably at the highest point of the year, 
since it was at about the close of the dry season, the rainy season 
beginning in June or July. 

SIZE. 

The general size of the clams caught for the canneries is 2J to 5 
inches, measured from the hinge ligament to the point opposite. 
Judging by the lines of growth upon the shells these clams vary in 
age from 3 to 7 years. The character of the dredge used in taking 
the clams is such that very few clams less than 2i inches in size are 
brought up. The canneries obtain their stock from tlie operators of 
the dredge, none being bought of hand operators. 

The clams exhibit two marked types of shell character. About 50 
per cent are thick shelled, the valves having thick lips, while about 
30 per cent are thin shelled with thin lips. The remaining 20 per 
cent are rather intermediate between these two types. These dis- 
tinctions may arise from the presence of two varieties of the species 
but most })robably are due merely to individual variation in the 
growth of the shell. 



DEAD SHELLS. 

Dead shells are found almost ever3^where on the clam bed. In some 
places they are very abundant while in others they are occasional. 
The action of the dredge" has probably little or nothing to do with 
this condition for the following reasons : 

1. The dead shells are found, in varying quantities, over almost the 
entire bar. 

2. The clam dredge has worked over but a ^mall portion of the bar 
and in but two localities. 

3. Practically all of the shells are unbroken, while many of them 
would most likely be otherwise had the dredge been responsible. 

4. By treading, several hundred chims weie dug in a locality where 
the dredge certainly had never operated. In this locality many dead 
shells were found. In some cases a single valve was found lying fiat 
on the bottom, while in many cases both valves were found intact, 
buried in the mud as iji life, but dead and filled with mud. 

From these facts it appears that the death of the clams is not due 
to the action of the dredge. The death rate is probably no greater 
than might be expected on a clam bed wdiere the temperature was such 
as to permit abundant development of the young and where the ten- 
dency would thus be for the population constantly to approach the 
maximum which could be supported by the available food supply. 
In such case any sudden lessening of the abundance of food, even 
though comparatively slight and of temporary duration, w^ould cause 
the death of a consideral)le number of clams. Furthermore, the per- 
centage of individuals dying from old age would not be inconsiderable 
in a population as dense as that described. 

SPAWNING. 

From a rather limited number of observations it would appear that 
the clams become sexually mature when about 3 inches in size, 
probably 2 years of age. According to information received locally 
the spawning season extends from about May 1 to xVugust 1. 

THE FUTURE OF THE CLAM INDUSTRY. 

The outlook for the clam industry in this region is very promis- 
ing. The raw material — that is, the clams — being very abundant 
and near at hand, and methods having been devised to prepare them 
into tasty products, the output is only limited by the capacity of the 
factories ^ and the efforts of their sales departments. The clam 
has never been exploited as has the oyster. There are people 
living in the interior who have never seen a live clam and know little 
of its merits. Those people who live on the coasts and anywhere near 
a section which yields clams invariably prefer them in the shell 
rather than canned. Canned clam products, therefore, need con- 
siderable advertising before they become universally known and ac- 

" Tbe dredge used on this clam bed is quite unlike the usual oyster dredge. It is carried 
on a large scow or boat resembling a house boat and consists of an elaborate piece of 
mechanism in the natuiv of an escalator which projects from beneath the boat with the 
lower end dragging over the bottom. The clams are dug from the bottom by spikes in an 
endless chain belt and drawn up a wooden trough or incline into the boat. 

''There are two ciinucrics at present, one bi'ing located at Marco and one at Casambas, 
both at the northern end of the clam beds. 



'ceptecl. But in spite of these facts the factories have been producing 
thousands of cases annually. A hirge part of this output is chim 
chowder and clam juice rather than canned whole clams. 

It is quite certain that as long as the dredge works efficiently hand 
digging, for the canneries will not be resorted to again. In order to 
maintain daily operations the factories must use a dependable and 
cheap method to obtain clams, for, because of the warm climate, no 
surphis stock of live clams is allowed to accumulate. It, therefore, 
can readily be seen that a dependable means of obtaining the clams 
is of the utmost importance to the efficient and profitable manage- 
ment of the factories. 

RECOMMENDATIONS. 

At the. present time there is no immediate danger of the beds 
becoming depleted, partly because of the great abundance of the 
clams and partly because there is but one dredge operating. 

There will probably bo more dredges in operation in the future and 
shoidd these be of great eifectiveness in digging the clams, it is xerj 
probable that sharp inroads would be made upon the most accessible 
bars. If this condition arises, measures of protection should be en- 
forced, among which the following may be suggested : 

1. The dredges should not be ])ermitted to operate in water less 
than 8 feet deep, mean tide. The present law of Florida requires 
that dredges may not operate in water less than 12 feet deep unless 
in an open sea where hand operatoi's could not w^ork because of 
weather conditions. In the locality in question practically all of the 
shallow bars are situated in the lee of the land. The i2-foot law 
would seem to work too much of a hardship on the dredgers in this 
vicinity. The bottom slopes very gradually along this part of the 
coast so that the 12-foot line would be about 5 miles offshore while 
the 8-foot line would be from 1 to 3 miles from shore. Prohibition 
of the dredges from digging on the most shallow bars would not 
benefit the few local settlers to any extent, but it would enable fisher- 
men from near-by towns to "tread" their clams and carry on their 
own independent businesses as is done by the few Key West diggers. 
At the present time there are very few clams taken in this manner 
and for this purpose, but the future may hold some possibilities 
along this line. 

2. The mininunu size of the clams which might legally be taken 
■ could be increased from 2 to 3 inches, measured from the hinge liga- 
ment to furthest opposite point. 

3. A closed season mightbe established throughout May and June, 
during which time the major portion of the clams are spawning or 
have spawned and are in poor condition. 

4. The catch of each dredge could be limited to a certain number 
of bushels per day or the operation of the dredge restricted to cer- 
tain periods of time. 

It would not be necessary to enforce all of these restrictions at the 
same time for should either Xos. 1, 3, or 4 be put into effect beneficial 
results would accrue. While No. 2 would be of value, the fact re- 
mains that at the present time by far the greatest percentage of 
<clams caught are 3 inches or more in size. 

WASHINGTON : GOVERNMENT I'ltlNTlNC (II-FUE : 102O 



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